【作者】 刘超；

【导师】 杨宗凯；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2005， 博士

【摘要】 多输入多输出(MIMO)系统是近十年来现代数字通信领域最重大的技术突破之一。该技术催生了许多先进通信技术,被认为是解决未来无线通信网络高速流量瓶颈的强有力竞争者。在MIMO 系统发明短短几年以后,就出现了采用该技术的大规模标准化驱动的商业无线产品和网络,例如宽带无线接入系统,无线局域网,3G和后3G 网络。MIMO 系统的优势在于其潜在容量巨大,且随着收发天线数目较小的一方呈线性增长。理论研究和实践应用都表明MIMO 系统是未来实现吉比特高速无线通信的重要技术手段,因此具有极高的研究价值。经过近十年的努力,MIMO 系统及其相关技术虽然已经获得很大发展,但仍然存在以下一些不足: (1) MIMO 系统容量的研究还不完善。现有研究大多基于瑞利分布信道的假设,然而在某些无线应用场合,例如宽带无线固定接入系统,往往适合采用莱斯信道模型。如何对这种多天线系统建模以及采用何种传输策略值得研究。(2) MIMO 系统检测问题还有待研究。为了逼近多天线系统的容量需要有好的检测技术。然而MIMO 系统在带来巨大容量的同时,也产生了极大的接收信号检测复杂度。球形解码算法是一种性能优化,复杂度适中的检测算法。但是常规球形解码算法不能解决发送天线大于接收天线的问题。已有的广义球形解码算法虽然能够克服球形解码算法的不足,但存在复杂度大的缺点。(3) MIMO 系统的联合检测解码问题需要改进。联合检测解码可以进一步提高系统的性能。如何将性能优化的球形解码算法和Turbo 迭代解码进行联合以进一步提高系统性能值得研究,其核心问题为如何构造一个软球形解码器。针对这些问题的研究,对于MIMO 系统理论的完善和相关技术的提高是必要且有价值的。在国家自然科学基金项目——“基于媒体传输特性的无线多媒体技术研究”(项目编号:60202005)的资助下,本文的研究工作从三个方面展开:(1)更多还原

【Abstract】 Digital communication using multiple-input–multipleoutput (MIMO) has recently emerged as one of the most significant technical breakthroughs in modern communications in the last two decades. The technology figures prominently on the list of recent technical advances with a chance of resolving the bottleneck of traffic capacity in future high speed wireless networks. Perhaps even more surprising is that just a few years after its invention the technology seems poised to penetrate large-scale standards-driven commercial wireless products and networks such as broadband wireless access systems, wireless local area networks (WLAN), third-generation (3G) networks and beyond. The advantage of MIMO system is its potential huge capacity, and the capacity increases linearly with the lesser number of the transmit and receive antennas. The theoretical research and practical application indicate that MIMO system is the important technology to realized the future high speed gigabit wireless communication, so it has high research value. After nearly ten years efforts, great development has been gained for MIMO system and its related technology. However, some disadvantages still exist: (1) The research on the MIMO capacity is not complete. The exist research is generally based on the rayleigh distribution assumption. However, in some case of wireless communications, such as the broadband wireless access system, the proper channeal model is the ricean channel model. How to model this multiple antenna system and what transmit scheme should be adopted is worth studying. (2) The detection problem for MIMO system needs further research. In order to approach the MIMO system capacity, good detection algorithm is needed. However the mimo system brings the huge capacity as well as high complexity of the receive signal detection. Sphere decoding algorithm is a detection algorithm with optimal performance and medium complexity. However, the exist sphere decoding algorithm can not solve the system where there are more transmit antennas then the receive antennas. The generalized sphere decoing algorithm could overcome the shortcomings of the sphere decoding algorithm, but the complexity is very high. (3) Joint the detection and decoding for MIMO system need to be improved. The joint detection and decoding can further improve the system performance. However how to combine the sphere decoding algorithm and Turbo iterative decoding to further improve the system performance need research. The core problem is how to construct a soft sphere decoder. The research focusing on these shortcomings is very important and valuable. Our research obtained support of the support of National Natural Science Foundation (Investigation of Wireless Multimedia Techniques based on Multimedia Transmission Property, No. 60202005). Our research work contains three categories: (1) the modeling and simulation of the ricean channel multiple antennas system adopting transmitted power optimal allotment; (2) the research on the fast generalized sphere decoding algorithm which is suitable for the cases where there are more transmit antennas then the receive antennas; (3) the soft generalized sphere decoder for the joint detection and decoding . The contribution of this thesis contains the following aspects: (1) propose the multiple-antenna system capacity model with ricean distribution, analysis the capacity with optimal transmit power allotment, and compare with the equal transmit power allotment with low complexity The conclusion could be helpful for the wireless communication system design. (2) Propose a new fast generalized sphere decoding algorithm. This algorithm usestwo regular sphere decoding algorithm to solve the cases where there are more transmit antennas then the receive antennas. It is very simple and easy to be implemented. We name this algorithm as double layer sphere decoding algorithm.; (3) Propose an improved double layere sphere decoder. This decoder can adjust its search radius according to the SNR change. Its performance is stable then the previous double layer sphere decoding algorithm; (4) Give a system model using joint sphere decoding algorithm and Turbo iterative decoding algorithm and propose a soft list generalized sphere decoder to be used in this model. This decoder can receive and produce the soft information. The simulation result shows that this system achieves the near-capacity of multiple-antenna system.更多还原